Telephone system



Oct. 1942. w H, r HOLDEN 2,299,898

TELEPHONE SYSTEM d NVE N TOR W H T HOLDEN By ,4 TTORNE V Oct. 27, 1942. w. H. T. HOLDEN TELEPHONE-SYSTEM Filed Oct. 16, 1941 4 Sheets-Sheefl 2 thumb am zzu WON @QN l PIA.

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Oct. 27, 1942. W H T HOLDEN 2,299,898

TELEPHONE SYSTEM Filed Oct. l5, 1941 v 4 Sheets-Sheet 5 T0 CHNNEL CONTROL CIRCUIT /A/VNTOR WH. f HOLDEN ATTORNEY Oct. 27, 1942. w. H. T. HOLDEN 2,299,898v

TELEPHONE SYSTEM Filed Oct. 1G, 1941 4 Sheets-Sheet 4 ATTORNEY Patented Oct. 27, 1942 UNITED STATES vPATENT OFFICE TELEPHONE SYSTEM William H. T. Holden, Woodside, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application Qctoher 16, 1941, Serial No. 415,226

6 Claims.

This invention relates to telephone systems and has for its object to simplify the selection of connecting circuits in such systems.

In the crossbar dial system, the extension of a connection from a calling line to a called line is controlled by common equipmentI known as senders and markers. Each connection takes place in two stages, one connecting the calling line by way of a district junctor to an outgoing trunk and the other connecting the trunkto the called line. In each stage the marker receives an indication of the identity of the originating and terminating circuits and connects therewith. It then tests for and selects an idle channel and operates the switches making up the channel to complete the connection between the originating andterminating circuits.

In accordance with the present invention improved means is provided for testing such channels.

More speciiically, the test conductors of the three links forming a channel are connected through rectiers to a common point and thence to start cathodes of a pair of multicathode gasfilled tubes. By means of a series of delay circuits the iirst idle channel is effective to operate the connected tubes which in turn identify the channel and connect the switch operating cir-` cuits through to the channel control circuits of the marker.

The invention will be more clearly understood from a considerationV of the following description read in connection with the drawings in which:

Fig. 1 shows a set of crossbar switches connecting district junctors with outgoing trunks, as well as the district and oiiice frame connectors; y

Fig.` 2 shows in diagrammatic form a sender and parts of a marker and the details of a part of the channel test circuit;

Fig. 3 shows the relays which connect the channel control circuit to the selected channel; and

Fig. 4 shows the gas-filled tubes for selecting and identifying an idle channel.

Fig. 3 should be placed at the right of Fig. 1`

with Figs. 2 and 4 be1ow Figs. 1 and 3, respectively.

This channel testing circuit is especially adapted for use in a crossbar dial system of the type disclosed and claimed in U. S. Patent 2,235,803, granted to W. W. Carpenter on March 18, 1941.

When a call is initiated, the calling line is automatically extended to an idle district junctor such as junctor |00 and through the associated sender link |0| to an idle sender 200. The designation of the wanted line is recorded in the sender which, as soon as `it has received the designation of the wanted oce, connects itself through the marker connector 20| to an idle marker including frame register 202 and the code registers 203. The oice code is transferred to the code registers 203 and is translated by means indicated as translator 204 to bring about the operation of a route relay 205. Route relay 205 at its left contact closes a circuit for operating the ofce frame connector represented by multicontact relay |02. With relay |02 operated, route relay 205 operates relay |03 to connect a group of trunks leading to the wanted oftice to the trunk test relays of the marker. For example, the test conductor |04 of trunk |05 is connected over contacts of relays |03 and |02 to the Winding of test relay 206. As set forth in the above-identiiied Carpenter patent, the trunkl test relays are arranged' in a chain and an idle trunk is selected by a circuit extending over the front contacts of busy trunk test relays and the back contact of the iirst idle test relay to the corresponding trunk select relay. Assuming that trunk |05 is idle and relay 206 unoperated, the idle trunk |05 is identied by the operation of relay 201.

Referring to Fig. 1 it will` be apparent that junctor |00 has access to twenty district links, of which links |06 to |09 have been indicated. Each of these links appears in a different one of the district secondary switches ||0 to H3. Similarly trunk |05 `has access to twenty omce links, of which links ||4 to are shown. Each of these oflice links appears in a diierent one of the oice primary switches |I8 to |2|. Each district frame is connected to every office frame by means of oice` junctors, one ofce junctor extending between a given district secondary switch and a given oiice primary switch. For example, ofce junctor |22 connects switch ||0 to switch IIB, junctor |23 connects switch ||2 to switch H9, etc. Therefore, between district junctor |00 and trunk |05 there are twenty channels, determined by the respective district and office frames and each comprising a particular district link, office junctor and oiice link, all of which must be idle to make the channel available for-use.`

`In order to test all of these elements, the marker must make a connection therewith. When the district junctor |00 was connected with the sender 200, a registration was made in the sender 200 of the number of the frame on which the district junctor was located and this registration was transferred to frame register 202 of the marker. Under the control of the frame register 202, the proper district frame connector is selected and a multicontact relay |30, individual to the marker, is operated. rlhe district junctor |00 operates a relay |3| common to the ten junctors appearing in the district primary switch |32. Relays I3| and |30 connect the test leads of the twenty district links |05 to |09, etc., through to the marker.

When oflice frame connector relay |02 operated, it closed a circuit for relay S which is individual to the cilice frame and which, in operating, closes a circuit from ground over conductor 230, contact of relay |30 to the winding of relay and battery. Relay |33 being operated under the joint control of means ndividual to the ffce and district frames may be used to select the group of oilice junctors |22 to connecting those frames and extend their test conductors to the marker.

When the idle trunk was selected by the operation of relay 227|, a circuit was closed from ground over a Contact of relay |02 to the winding of relay |34 and battery. Relays |34 and |02 extend the test conductors of the office links I I4 to I I1 to the marker.

When the above-traced connections have been made the channels are tested. The circuits .for testing the channel comprising district link |09, ofce junctor |25 andV oice link' ||4 have been shown in detail.

The test circuit of district link |09 extends over contacts of relays I3I and |30 to conductor |35, and cuprous oxide rectiiier or varistor 2|0; the test circuit of ofce junctor |25 extends over contacts of relays |33 and |30 to conductor |35 and varistor 2II; the test circuit of oice link I|4 extends over contacts of relays |34 and |02 to conductor |31 and varistor 2|2. The varistors 2|0, 2 II and 2I2 are connected together and to the channel test conductor 2|6.

rI'he other channels have their elements connected to similar channel test circuits shown schematically at 2|'|, 2I8 and 2|9. Conductor 220, connected through varistor 2|3 in parallel with conductors |35, |36` and |31 maybe grounded from a pattern relay, the function of which is to mark channels unavailable as described in the above-identied Carpenter patent.

Channel test conductor 2|6 is connected to a delay network 2 I4' which in turn is connected in parallel to two identical T' networks 22| and 222.

Conductors 224 and` 225 outgoing from networks 22| and 222, respectively, are connected to individual starting cathodes in two sets of multielement gas-lled tubes. The five tubes 40| to 405 each have four starting cathodes thus providing one starting cathode per channel. The four tubes 4| I to 4I4 each have five starting cath-- odes, thus also providing one starting cathode per channel. Each channel test conductor is connected to one starting cathode in each set, the conductors connected to one tube in one set being connected to different tubes of the second set so that each channel is associated with a different pair of tubes.

The starting anodes of the tubes in each set are connected together and to a 50-volt positive battery through the 100,000 ohm resistances 430 and 43|.

As set forth in the above-mentioned Carpenter patent, busy channel elements are grounded, While idle channel elements are connected to a negative battery of approximately volts. If any element is grounded, the potential on test conductor 2 IIS is reduced nearly to zero. The delay networks 2I4, etc. provide slightly different delays for each channel so as to create an order of preference for the channels. Therefore the idle channel having the shortest delay will permit the starting gaps in the corresponding tubes to break down, which thereby prevents the breakdown of any other tubes.

Assuming the channel connected to test conductor 2 I0 is idle and has the shortest delay, the start gap between start anode 406 and start cathode 401' breaks down, causing the main gap to break down and complete a circuit from ground on main cathode 408 through the main gap to main anode 408, conductor 4H), winding of relay 300 to source 320, supplying a pulsating current of superimposed alternating and direct current. Relay 330 connects negative battery through resistance 32| over its inner contact to conductor 322 and electrode 420 of tube 42|, locking the tube operated.

Similarly, the starting gap between start anode 4i5 and start cathode 4|3 breaks down, completing a circuit from ground on main cathode 4|? through the main gap to main anode 4|8, conductor 499, winding of relay 3I0 to a source 323 similar to source 320. Relay 3|0 connects battery through resistance 324 over its inner contact to conductor 325 and electrode 42| of tube 4| I, locking that tube. Relays 3|0 and 300 are equipped with copper sleeves so that they can operate and hold in series with the pulsating current supply.

Each of the relays 3I0 to 3I3 operated from tubes 4I I to 424 connect five sets of channel test leads to the armatures of relays 300 to 304, While the operation of one of the relays 300 to 304 connects one set of channel test leads to the channel control circuit. By this arrangement nine tubes and nine relays are employed to perform the function of the sixty relays employed in the cited Carpenter patent.

It is, of course, to be understood that other tube and relay arrangements may be used without departing from the spirit of the invention.

When the channel control circuit connects ground to the channel test leads to operate the switch magnets, relays 340, 34| and 342 operate, connecting ground over their contacts in series to r-esistances 32| and 324 to quench the tubes and release the marker. These relays are slow to operate, so that the magnets may be locked before their operating circuits are opened.

What is claimed is:

l. In a telephone system, incoming circuits and outgoing circuits, a plurality of channels each comprising a plurality of sections for connecting an incoming circuit to an outgoing circuit, a test conductor for each of said channel sections, means for marking said section test conductors as busy or idle, and means for testing each channel comprising means for connecting the test conductor of each channel section to a unidirectional current carrying device, the devices connected with sections of the same channel being arranged to be conductive in the same direction and connected in multiple to a channel test conductor, gas-filled tube means connected to said channel test conductors, means to supply starting potential to said gas-lled tube means when all sections of the channel are marked idle and means to selectively operate said gas-lled tube means to identify an idle channel.

2. In a telephone system, incoming circuits and outgoing circuits, a plurality of channels each comprising a plurality of sections for connecting an incoming circuit to an outgoing circuit, a test conductor for each of said channel sections, means for marking said section test conductors as busy or idle, and means for testing each channel comprising means for connecting the test conducto-r of each channel section to a unidirectional current carrying device, the devices connected with sections of the same channel being arranged to be conductive in the same direction and connected in multiple to a channel test conductor,` gas-filled tube means connected to said channel test conductors, means to supply starting potential to said gas-filled tube means when all sections of the channel are marked idle, delay circuits interposed in said channel test conductors, said delay circuits having different Deriods to set up a preference relationship between said channels and means to selectively operate said gas-nlled tube means to identify an idle channel.

3. In a telephone system, incoming circuits and outgoing circuits,` a pluralityk of channels each comprising a plurality of sections for connecting an incoming circuit to an outgoing circuit, va test conductor for each of said channel sections, means for marking said section test conductors as busy or idle, and means for testing each channel comprising means for connecting the test conductor of each channel section to a unidirectional current carrying device, the devices connected with sections of the same channel being arranged to be conductive in the same direction and connected in multiple to a channel test conductor, two sets of gas-filled tubes, means controlled over said channel test conductors to operate one tube in each of said sets and means under the control of said operated tubes to select an idle channel.

4. In a telephone system, incoming circuits and outgoing circuits, a plurality of channels each comprising a plurality of sections for connecting an incoming circuit to an outgoing circuit, a

test conductor for each of said channel sections,

means for marking said section test conductors as busy or idle, and means for testing each channel comprising means for connecting thel test conductor of each channel section to a unidirectional current carrying device, the devices con-- nected with sections of the same channel being arranged to be conductive in the same direction and connected in multiple to a channel test con? ductor, two sets of gas-filled tubes, means controlled over said channel test conductors to operate one tube in each of said sets to identify an idle channel, channel operating circuits and means under the joint control of said operated tubes to connect the section test conductors of said identified channel with said channel operating circuits.

5. In a telephone system, incoming circuits and outgoing circuits, a plurality of channels each comprising a plurality of sections for connecting an incoming circuit to an outgoing circuit, a test conductor for each of said channel sections, means for marking said section test conductors as busy or idle, and means for testing each channel comprising means for connecting the test conductor of each channel section to a unidirectional current carrying device, the devices connected with sections of the same channel being arranged to be conductive in the same direction and connected in multiple to a channel test conductor, gas-filled tube means connected to said channel test conductors, means to supply starting potential for said gas-lled tube means to said channel test conductors from the idle channel sections connected therewith, means controlled from busy channel sections to render in-` eiective the potential supplied to the channel test conductors connected therewith, and means to selectively operate said gas-nlled tube means connected with a channel, all sections `of which are idle.

6. In a telephone system, incoming circuits and outgoing circuits, a plurality of channels each comprising a plurality of sections for connecting an incoming circuit to an outgoing circuit, a test conductor for each of said channel sections, means for marking said section test conductors as idle by connecting negative battery thereto and busy by connecting ground thereto, and means for testing each channel comprising means for connecting the test conductor of each channel section to a unidirectional current carrying device, the ydevices connected with sections of the same channel being arranged to be conductive in the same direction and connected in multiple to a channeltest conductor, gas-filled tube `means connected to said channel test conductors, means to supply starting potential for said gas-filled tube means to said channel test conductors from the negative battery on the idle channel sections connected therewith, means controlled from busy channel sections to connect ground to the channel test conductors to render ineffective the negative potential connected thereto, and means to selectively operate said gaslled tube means connected with a channel, all sections of which are idle.

WILLIAM H. T. HOLDEN. 

